<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        div {
            width: 100px;
            height: 100px;
            background-color: #f00;

            /* 实现元素之间的相互转化 */
            /* display: inline; */

            /* display: inline-block; */
        }

        span {
            width: 100px;
            height: 100px;
            background-color: #ff0;
            display: block;
        }
    </style>
</head>

<body>

    <div></div>

    <span></span>

</body>

</html>